The invention relates to a hybrid pump for delivering a liquid pump medium.
In the present case, a hybrid pump is understood to mean a pump that operates in a first mode as a displacement machine and in a second mode as a continuous-flow machine, in order to combine the respective advantages of these two pump types.
A known hybrid pump (DE 101 58 146 A1) has a housing that is equipped with an inlet, an outlet and a pump space. In cross section, the pump space has a substantially round or rounded running surface for a rotor with rotor blades that is rotatable about a rotor axis, and a respective side face on each side of the rotor. The rotor is arranged eccentrically in the pump space, wherein each of the rotor blades is also movable relative to the rotor. Together with the running surface of the pump space, the rotor blades define a plurality of pump chambers. In one embodiment, it is provided that at least the inlet is arranged in the side face of the pump space.
The fact that the filling and emptying of the pump chambers during the pumping operation is not optimal is problematic in the known hybrid pump. It was possible to demonstrate, for instance, that the pump medium is only slightly exchanged in the part of the pump chambers facing the rotor axis. This was not significantly improved by the arrangement of the inlet or the outlet in the side face of the pump chamber. The volume of the pump chambers is thus only insufficiently used in the pumping operation.
It must also be taken into account that the arrangement of the inlet or the outlet in the side face of the pump chamber is fundamentally linked to a deflection of the pump medium by roughly 90°, depending on the design. At least in the part of the pump chambers facing the rotor axis, this leads to the formation of a dead space that is not utilized in the filling of the pump chambers. This leads to an insufficient filling of the pump chambers. The resulting efficiency of this pump is low.
The above-explained, known hybrid pump has already been configured and refined in regard to improved efficiency (DE 20 2005 007 789 U1), specifically, by using a rotor consisting of chemically-resistant, essentially inelastic plastic, in particular, PEEK, and having a baseplate, on which the stationary rotor parts are fixedly mounted, that is associated with one side face of the pump space. A curved rotor blade is pivotably hinged to the outer end of each stationary rotor part. Between adjacent rotor parts and rotor blades, the pump chambers of the rotor are formed, which are opened towards the upper side face of the pump chamber as previously, but closed off by the baseplate.
In the above-explained prior art, from which the invention proceeds, the design of the rotor is used to arrange the inlet or the outlet in the upper side face of the pump space in such a manner that the geometric rotor axis runs through the inlet or the outlet.
The flow path of the pump medium first runs along the rotor axis and then into the respective pump chamber. This has the effect that the pump chambers are filled at least in part from a position that is as close as possible to the rotor axis. The rotor is thus penetrated by the pump medium in a certain sense. The above-described formation of a dead space in the pump chambers can thereby be largely avoided. Consequently, the quality of the filling of the pump chambers during pumping operation increases.
Structurally, it is necessary in the solution proposed to construct a part of the area surrounding the rotor axis with a hollow shape, at least over part of the axis, in order to be able to use this area as an inlet. A number of design possibilities exist for this, wherein it must be taken into account that a short circuit between the inlet and outlet must be avoided.
A rotor of the above-described type that is penetrated to a certain extent by the pump medium cannot be used in all circumstances for a hybrid pump. The teaching of the present invention is therefore based on the problem of increasing the efficiency of the known pump with a rotor having a baseplate, without constructing a part of the area surrounding the geometric rotor axis with a hollow shape.